Heating, ventilation, and air conditioning system boiler controller

ABSTRACT

Heating, ventilation, and air conditioning (HVAC) system boiler controllers are described herein. One controller includes a memory and a processor configured to execute executable instructions stored in the memory to determine a change to a set point of the boiler that would lower a cost of operating the boiler, determine whether the change to the set point of the boiler is possible for the boiler, and make the change to the set point of the boiler upon determining the change is possible.

PRIORITY INFORMATION

This application is a Continuation of U.S. application Ser. No.14/682,273, filed Apr. 9, 2015, the contents of which are incorporatedherein by reference.

TECHNICAL FIELD

The present disclosure relates to heating, ventilation, and airconditioning system boiler controllers.

BACKGROUND

A heating, ventilation, and air conditioning (HVAC) system can be usedto control the environment of a building. For example, an HVAC systemcan be used to control the air temperature, humidity, and/or air qualityof a building.

One of the major energy consumers of an HVAC system is a boiler (e.g.,boiler plant). Reducing the energy consumption of the boiler of an HVACsystem can reduce the energy consumption, and therefore reduce theoperational cost, of the HVAC system.

The energy consumption of a boiler plant may depend on the set points ofthe boiler, such as the supply water temperature and the pump speed, forexample. In previous approaches, the set points of the boiler may befixed (e.g., may not change during operation of the boiler), or may bedetermined (e.g., changed during operation of the boiler) based on resetcurves (e.g., based on the outside air temperature) or an estimate ofthe current heat demand of the HVAC system and/or building.

However, fixing the boiler set points or determining the boiler setpoints based on reset curves may be ineffective at reducing the energyconsumption of the boiler. Further, determining the boiler set pointsbased on a current heat demand estimate may be difficult, as theavailability of the information needed to do so may be limited.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates an HVAC system boiler in accordance with one or moreembodiments of the present disclosure.

FIG. 1B illustrates an HVAC system boiler controller in accordance withone or more embodiments of the present disclosure.

FIG. 2A illustrates an example of a model of the relationship between anumber of controlled variables of a boiler and a manipulated variable ofthe boiler in accordance with one or more embodiments of the presentdisclosure.

FIG. 2B illustrates an example of a model of the relationship betweenthe cost of operating the boiler and the manipulated variable and theoperating condition of the boiler in accordance with one or moreembodiments of the present disclosure.

FIG. 3 illustrates a graph of an example of incremental changes made tothe set points of two controlled variables of a boiler in accordancewith one or more embodiments of the present disclosure.

DETAILED DESCRIPTION

Heating, ventilation, and air conditioning (HVAC) system boilercontrollers are described herein. For example, one or more embodimentsinclude a memory and a processor configured to execute executableinstructions stored in the memory to determine a change to a set pointof the boiler that would lower a cost of operating the boiler, determinewhether the change to the set point of the boiler is possible for theboiler, and make the change to the set point of the boiler upondetermining the change is possible.

HVAC system boiler controllers in accordance with the present disclosurecan determine and/or change (e.g., adjust) the set point(s) of a boilersuch that the energy consumption, and therefore the operational cost, ofthe boiler (e.g., of the HVAC system) is effectively reduced. That is,determining and/or changing the set point(s) of a boiler in accordancewith the present disclosure can effectively reduce the energyconsumption, and therefore effectively reduce the operational cost, ofthe boiler.

Further, HVAC system boiler controllers in accordance with the presentdisclosure may determine and/or change the set point(s) of the boilerutilizing information (e.g., data) readily available to the controller.As such, HVAC system boiler controllers in accordance with the presentdisclosure may be able to determine and/or change the set point(s) ofthe boiler in a quicker, more accurate, and/or easier manner thanprevious approaches.

In the following detailed description, reference is made to theaccompanying drawings that form a part hereof. The drawings show by wayof illustration how one or more embodiments of the disclosure may bepracticed.

These embodiments are described in sufficient detail to enable those ofordinary skill in the art to practice one or more embodiments of thisdisclosure. It is to be understood that other embodiments may beutilized and that mechanical, electrical, and/or process changes may bemade without departing from the scope of the present disclosure.

As will be appreciated, elements shown in the various embodiments hereincan be added, exchanged, combined, and/or eliminated so as to provide anumber of additional embodiments of the present disclosure. Theproportion and the relative scale of the elements provided in thefigures are intended to illustrate the embodiments of the presentdisclosure, and should not be taken in a limiting sense.

The figures herein follow a numbering convention in which the firstdigit or digits correspond to the drawing figure number and theremaining digits identify an element or component in the drawing.Similar elements or components between different figures may beidentified by the use of similar digits.

As used herein, “a” or “a number of” something can refer to one or moresuch things. For example, “a number of manipulated variables” can referto one or more manipulated variables.

FIG. 1A illustrates a heating, ventilation, and air conditioning (HVAC)system boiler 100 in accordance with one or more embodiments of thepresent disclosure, and FIG. 1B illustrates an HVAC system boilercontroller 102 in accordance with one or more embodiments of the presentdisclosure. That is, FIG. 1B illustrates a controller 102 for a boiler100 (e.g., a boiler plant that includes boiler 100 and a number of waterpumps) of an HVAC system illustrated in FIG. 1A.

In the embodiment illustrated in FIG. 1A, controller 102 is included in(e.g., located within) boiler 100. However, embodiments of the presentdisclosure are not so limited. For example, in some embodiments,controller 102 may be separate from (e.g., located outside of) boiler100. That is, in some embodiments, controller 102 can be a stand-alonedevice.

As shown in FIG. 1A, boiler 100 can include a heat exchanger 191 and aburner 192. The burner 192 can output heat to a heat exchanger 191 andflue gas to an external pre-heater 193. Supply water 194 (e.g., at aparticular temperature T_(SW) 184) can be output from the heat exchanger191 and the water can return 195 (e.g., at a particular temperatureT_(RW) 185) through a water pump 196 to the pre-heater 193 and back tothe heat exchanger 191 of the boiler 100.

As shown in FIG. 1A, boiler 100 can include a valve 188 and a fan 190(and, in some embodiments, a damper). Controller 102 can control theposition of the valve 188, speed of the fan 190, and/or position of thedamper. Based on the various controlled positions and/or speeds, fuel(e.g., gas) 181 can be input to the burner 192 of the boiler 100. Therate of fuel input can be controlled by the valve position, damperposition, and/or speed of the fan 190.

The fan 190 can include a variable-frequency drive (VFD) fan or aconstant-frequency drive (CFD) fan, among other fans. For instance, aCFD fan can include a damper. Combustion air (e.g., outdoor air) can beinput to the VFD fan, or input to the CFD fan, and then sent to thedamper.

As illustrated by FIG. 1A, the input fuel 181 can be measured by a fuelconsumption sensor 182 to determine total fuel consumption 183 of boiler100. Further, a temperature sensor (not shown in FIG. 1A) can measurethe supply water temperature 184 (e.g., T_(SW)). The temperature sensorcan send the measured supply water temperature 184 to the controller102.

The controller 102 can determine a difference in the supply watertemperature 184 and a supply water temperature set point. The supplywater temperature set point may be determined and/or changed bycontroller 102, as will be further described herein. Based on thedifference and/or change, the controller 102 can perform a controlaction (e.g., increase/decrease fan speed, or open/close a damper).

Controller 102 can control the operation (e.g., the operatingparameters) of boiler 100. For example, boiler 100 may have a number ofmanipulated variables and a number of controlled variables associatedtherewith. The controlled variables can be the variables of boiler 100that controller 102 is attempting to control (e.g., set and/or change).For instance, the controlled variables can include the supply watertemperature and/or pump speed of boiler 100. The manipulated variablescan be the operating parameters for boiler 100, which can control thecontrolled variables of the boiler. For instance, the manipulatedvariables can include the firing rate of boiler 100. That is, controller102 can control the manipulated variables of boiler 100, which in turncan control the controlled variables of the boiler. For instance,controller 102 can determine, and make changes to, the set points of thecontrolled variables of boiler 100, as will be further described herein.

As shown in FIG. 1B, controller 102 can include a memory 114 and aprocessor 112. Memory 114 can be any type of storage medium that can beaccessed by processor 112 to perform various examples of the presentdisclosure. For example, memory 114 can be a non-transitory computerreadable medium having computer readable instructions (e.g., computerprogram instructions) stored thereon that are executable by processor112 to determine, and make changes to, the set points of the controlledvariables of boiler 100 in accordance with the present disclosure. Thatis, processor 112 can execute the executable instructions stored inmemory 114 to determine, and make changes to, the set points of thecontrolled variables of boiler 100 in accordance with the presentdisclosure.

Memory 114 can be volatile or nonvolatile memory. Memory 114 can also beremovable (e.g., portable) memory, or non-removable (e.g., internal)memory. For example, memory 114 can be random access memory (RAM) (e.g.,dynamic random access memory (DRAM) and/or phase change random accessmemory (PCRAM)), read-only memory (ROM) (e.g., electrically erasableprogrammable read-only memory (EEPROM) and/or compact-disk read-onlymemory (CD-ROM)), flash memory, a laser disk, a digital versatile disk(DVD) or other optical disk storage, and/or a magnetic medium such asmagnetic cassettes, tapes, or disks, among other types of memory.

Further, although memory 114 is illustrated as being located incontroller 102, embodiments of the present disclosure are not solimited. For example, memory 114 can also be located internal to anothercomputing resource (e.g., enabling computer readable instructions to bedownloaded over the Internet or another wired or wireless connection).

As shown in FIG. 1B, controller 102 includes a user interface 116. Auser (e.g., operator) of controller 102 (e.g., boiler 100), such as, forinstance, a field engineer or technician for the HVAC system thatincludes boiler 100, can interact with controller 102 via user interface116. For example, user interface 116 can provide (e.g., display and/orpresent) information to the user of controller 102, and/or receiveinformation from (e.g., input by) the user of controller 102. Forinstance, in some embodiments, user interface 116 can be a graphicaluser interface (GUI) that can include a display (e.g., a screen) thatcan provide and/or receive information to and/or from the user ofcontroller 102. The display can be, for instance, a touch-screen (e.g.,the GUI can include touch-screen capabilities). As an additionalexample, user interface 116 can include a keyboard and/or mouse the usercan use to input information into controller 102. Embodiments of thepresent disclosure, however, are not limited to a particular type(s) ofuser interface.

As shown in FIG. 1B, controller 102 can include a set point optimizermodule 118, a set point tracker module 120, and an estimator module 122.As described herein, a “module” can include computer readableinstructions that can be executed by a processing resource (e.g.,processor 112) to perform a particular function. A module can alsoinclude hardware, firmware, and/or logic that can perform a particularfunction. As used herein, “logic” is an alternative or additionalprocessing resource to execute the actions and/or functions, describedherein, which includes hardware (e.g., various forms of transistorlogic, application specific integrated circuits (ASICs)), as opposed tocomputer executable instructions (e.g., software, firmware) stored inmemory and executable by a processing resource.

Estimator module 122 can determine (e.g., generate and/or build) and/orinclude (e.g., store) two different models (e.g., static models). Thefirst model 165 can be a model (e.g., mapping) of the relationshipbetween a number of controlled variables of boiler 100 and a number ofmanipulated variables and operating conditions (e.g., disturbances) ofboiler 100. The second model 166 can be a model (e.g., mapping) of therelationship between the cost of operating boiler 100 and the number ofmanipulated variables and operating conditions of boiler 100.

As an example, the first model 165 can include a look up table thatincludes values of the controlled variables for different values of themanipulated variables and different operating conditions, and the secondmodel 166 can include a look up table that includes the cost ofoperating the boiler for different values of the manipulated variablesand different operating conditions. The models, however, are not limitedto look up tables. For example, in some embodiments, the models can befunctions, such as multivariate static functions or radial basisfunctions, among other types of functions. Examples of the models willbe further described herein (e.g., in connection with FIGS. 2A-2B).

The controlled variables can include, for example, the supply watertemperature and/or pump speed of boiler 100. The manipulated variablescan include, for example, the firing rate of boiler 100. The operatingconditions can include, for example, outside air temperature and/or thepump speed of boiler 100 (e.g., in some embodiments pump speed may be acontrolled variable, and in some embodiments pump speed may be adisturbance) and/or return water temperature. The cost of operatingboiler 100 can correspond to, for example, the energy consumption ofboiler 100.

In some embodiments, estimator module 122 can determine (e.g., generate,build, update, and/or adjust) the models based on real time operationaldata and/or behavior of boiler 100 received by controller 102, such as,for instance, the supply and/or return water temperatures of boiler 100,the pump speed of boiler 100, and/or the firing rate of boiler 100. Forexample, estimator module 122 can determine the models from the realtime data using generally known recursive identification methods, suchas, for instance, a recursive least squares method, as will beappreciated by one of skill in the art. As such, estimator module 122can determine the models utilizing information (e.g., data) that isreadily available to and/or already being utilized by controller 102.

As an example, the supply water temperature set point, the return watertemperature, and the pump speed can be input into first model 165, andthe firing rate and the pump speed can be input into second model 166.Further, the fuel consumption of boiler 100, and the price of the fuel,can also be input into estimator module 122. In such an example, firstmodel 165 can be used to determine (e.g., output) the estimated steadyfiring rate for the boiler, and second model 166 can be used todetermine (e.g., output) the cost.

In some embodiments, estimator module 122 can receive (e.g., via userinterface 116) the models from the user (e.g., operator) of controller102. For instance, the models may initially be input into estimatormodule 122 by the user, and then subsequently may be updated and/oradjusted during operation of boiler 100 based on the real timeoperational data and/or behavior of boiler 100.

In some embodiments, the models can be pre-engineered models. Forinstance, estimator module 122 can initially determine (e.g., buildand/or generate) the models based on initial values for the controlledvariables, manipulated variables, and disturbances input into estimatormodule 122 during commissioning of controller 102, and then subsequentlyupdate and/or adjust the models during operation of boiler 100 based onthe real time operational data and/or behavior of boiler 100.

During operation of boiler 100, set point optimizer module 118 candetermine a change to a number of set points of boiler 100 (e.g., achange to the set points of a number of the controlled variables of theboiler) that would lower (e.g., reduce) the cost of operating boiler 100(e.g., that would lower the energy consumption of the boiler), and makethe determined change(s) to the set point(s). For example, set pointoptimizer module 118 can determine whether the change(s) to the setpoint(s) is possible (e.g., feasible) for the boiler (e.g., whether itwould be possible for the boiler to make the change(s)), and make thechange(s) to the set point(s) upon determining the change(s) ispossible. If the change(s) are determined to not be possible for theboiler (e.g., if the determined change(s) would be outside the operatinglimits of the boiler), set point optimizer module 118 may not make thechange(s), and may attempt to determine an additional (e.g., different)change(s) that would lower the cost of operating boiler 100 and bepossible for the boiler to make.

The number of set points of boiler 100 can include, for example, the setpoint of the supply water temperature of the boiler and/or the set pointof the pump speed of the boiler. Set point optimizer module 118 candetermine the change(s) to the set point(s) using the models determinedby and/or included in estimator module 122. In determining the change(s)to the set point(s), set point optimizer module 118 may assume theenergy consumption of boiler 100 is a static function of the manipulatedvariables and operating conditions of the boiler.

In instances in which optimizer module 118 determines changes to asingle (e.g., one) set point, optimizer module 118 can make the changeto the set point without making a change to any other set points ofboiler 100. For example, if optimizer module 118 determines a reduction(e.g., a feasible reduction) of the set point of the supply watertemperature of boiler 100 that would lower the cost of operating theboiler, the optimizer module may make this reduction while maintainingthe same pump speed of the boiler.

In instances in which optimizer module 118 determines changes to aplurality of set points (e.g., more than one set point), optimizermodule 118 can make the changes incrementally using incrementaloptimizer 161. That is, in such instances, the change to one set pointwould not be made until after the change to the previous set point iscompleted. For instance, the changes to the plurality of set points maybe made such that there is a delay between each respective change, inorder to minimize the transients induced by the changes. The length ofthe delay between each respective change may be determined by delaycalculation module 162.

As an example, if optimizer module 118 determines a reduction (e.g., afeasible reduction) of the set point of the supply water temperature andan increase (e.g., a feasible increase) of the set point of the pumpspeed of boiler 100 that would lower the cost of operating the boiler,the optimizer module (e.g., incremental optimizer 161) may first reducethe supply water temperature set point, wait for the supply watertemperature to cool to the reduced set point, and then increase the pumpspeed set point. The length (e.g., amount of time) of the delay betweenthe set point changes may be determined by delay calculation module 162,and may based on (e.g., be inversely proportional to) the pump speed ofboiler 100, and/or may depend on the pipe length and/or diameter of theHVAC system. An example of such incremental set point changes will befurther described herein (e.g., in connection with FIG. 3).

During operation of boiler 100, controller 102 may receive an indication(e.g., a warning) that the HVAC system (e.g., one or more circuits ofthe HVAC system) is receiving insufficient heat. As an example, outsidethe boiler controller, signals from the controllers of different boilerloads (e.g., air handling units, fan coils, variable air volume boxes,etc.) can be collected and checked against symptoms of insufficientheating (e.g., finding the most open heating valve of fan coil units,checking the saturation of zone controllers, etc.). If at least one suchsymptom is detected, controller 102 may receive an insufficient heatindication (e.g., an insufficient heat signal for the boiler may be setto true). As an additional example, if no such signal is available fromoutside the boiler controller, the boiler controller may build its ownsignal by estimating the heat demand from the difference between thesupply and return water temperatures and pump speed, and monitoring itsresponse to the set point changes.

In such examples, optimizer module 118 may determine (e.g., using themodels of estimator module 122) changes (e.g., additional changes) tothe number of set points of boiler 100 that would provide sufficientheat to the HVAC system (e.g., to the circuit(s) of the HVAC systemreceiving insufficient heat), and make (e.g., using incrementaloptimizer 161) the determined change(s) to the set point(s) (e.g., upondetermining the change(s) is possible). In instances in which optimizermodule 118 determines changes to a single set point, optimizer module118 can make the change to the set point without making a change to anyother set points of boiler 100, and in instances in which optimizermodule 118 determines changes to a plurality of set points, optimizermodule 118 (e.g., incremental optimizer 161) can make the changesincrementally, as previously described herein. An example of suchincremental set point changes will be further described herein (e.g., inconnection with FIG. 3).

As an example, the current set point of the supply water temperature,the current pump speed, and a heat demand signal can be input intoincremental optimizer 161. Further, the current pump speed can be inputinto delay calculation module 162. In such an example, incrementaloptimizer 161 can determine (e.g., output) a new supply watertemperature set point and a new pump speed that would lower the cost ofoperating the boiler while providing sufficient heat to the HVAC system,and delay calculation module 162 can determine (e.g., output) the delayneeded between the change of the supply water temperature set point andthe change of the pump speed. Incremental optimizer 161 can then makethe changes to the supply water temperature set point and pump speedincrementally, according to the delay determined by delay calculationmodule 162.

During operation of boiler 100, set point tracker module 120 can receivethe determined set point change(s) from set point optimizer module 118,and track the changed set point(s) using the first model of estimatormodule 122 (e.g., using the look up table that includes values of thecontrolled variables for different values of the manipulated variablesand different operating conditions). That is, after set point optimizermodule 118 determines the set point change(s), set point tracker module120 can ensure the operation of boiler 100 maintains the controlledvariable(s) at the changed set point using the first model of estimatormodule 122 (e.g., using the look up table). For instance, set pointtracker module 120 can set and/or adjust the operating parameters ofboiler 100 (e.g., the operating parameters of the manipulated variablesof the boiler) such that the controlled variable(s) is maintained at thechanged set point. That is, the first model of estimator module 122 canbe used as a static feedforward by set point tracker module 120.

As an example, set point tracker module 120 can receive the estimatedsteady firing rate for the boiler from first model 165, and the supplywater temperature and the set point of the supply water temperature canbe input into feedback controller 164 of set point tracker module 120.Feedback controller 164 can determine (e.g., output) the firing rate ofthe boiler, which can then be input into fuel-air ratio module 163 ofset point tracker module 120. Fuel-air ratio module 163 can thendetermine (e.g., output) a valve command for valve 188 and a fan/dampercommand for fan 190 that will ensure boiler 100 maintains the supplywater temperature at the set point. In some embodiments, the output ofthe feedback controller 164 can be based, for example, not only on theset point and measured supply temperature, but also on an estimatedfiring rate.

FIG. 2A illustrates an example of a model 232 of the relationshipbetween a number of controlled variables of a boiler and a manipulatedvariable of the boiler for a constant operating condition (e.g.,disturbance) of the boiler. As used herein, a constant operatingcondition can refer to a single operating condition (e.g., a pumpconstantly running at 2000 rpm), or an operating condition that fallswithin a particular range or set of possible operating conditions (e.g.,a variable speed pump that may run from 1000-4000 rpm). FIG. 2Billustrates an example of a model 240 of the relationship between thecost of operating the boiler and the manipulated variable and theoperating condition of the boiler. The boiler can be, for example,boiler 100 previously described in connection with FIGS. 1A and 1B.Models 232 and 240 can be determined by and/or included in estimatormodule 122 previously described in connection with FIG. 1B, and can beused by set point optimizer module 118 to determine changes to the setpoints of the controlled variables that would lower the cost ofoperating the boiler, as previously described in connection with FIG.1B.

In the example illustrated in FIGS. 2A and 2B, the controlled variableis the supply water temperature of the boiler, the manipulated variableis the firing rate of the boiler, and the operating conditions are thereturn water temperature and pump speed of the boiler. However,embodiments of the present disclosure are not limited to this controlvariable, manipulated variable, and disturbance combination.

In the example illustrated in FIG. 2A, the number of data points plottedin graph 230 are used to generate model 232. Each data point canrepresent the supply water temperature, the return water temperature,and the firing rate of the boiler at a different point in time duringthe operation of the boiler, and can be determined and/or received bythe boiler in real time. As such, model 232 can be used to determinewhat firing rate can be used by the boiler to generate a particular(e.g., desired) supply water temperature. In the example illustrated inFIG. 2A, the pump speed of the boiler is assumed to remain constant.

In the example illustrated in FIG. 2B, model 240 includes a plot 242 ofthe cost of operating the boiler at different firing rates, and a plot244 of the cost of operating the boiler at different pump speeds. Assuch, model 240 can be used to determine what the cost of operating theboiler would be for a particular firing rate and pump speed of theboiler.

FIG. 3 illustrates a graph 350 of an example of incremental changes madeto the set points of two controlled variables of a boiler in accordancewith one or more embodiments of the present disclosure. For example,line 352 represents the set point of the supply water temperature of theboiler over time, and line 354 represents the set point of the pumpspeed of the boiler over time. The boiler can be, for example, boiler100 previously described in connection with FIGS. 1A and 1B, and theincremental changes to the set points can be made by set point optimizermodule 118 during operation of the boiler, as previously described inconnection with FIG. 1B.

For example, during operation of the boiler (e.g., after an initial timet0), set point optimizer module 118 may determine a possible (e.g.,feasible) reduction of the set point of the supply water temperature ofthe boiler that would lower the cost of operating the boiler. Thisreduction can be made (e.g., by the set point optimizer module) at timet1, as illustrated in FIG. 3. However, the pump speed of the boiler maybe maintained at the same speed as before time t1, as illustrated inFIG. 3.

During subsequent operation of the boiler (e.g., after time t1), setpoint optimizer module 118 may determine a possible (e.g., feasible)reduction of the set point of the supply water temperature of the boilerand a possible increase of the set point of the pump speed of the boilerthat, in combination, would further lower the cost of operating theboiler. However, as previously described herein (e.g., in connectionwith FIGS. 1A and 1B), these set point changes may need to be madeincrementally. As such, the set point optimizer module may first reducethe supply water temperature set point at time t2, and then, after adelay (e.g., for the supply water temperature to cool to the reduced setpoint), increase the pump speed set point at time t3, as illustrated inFIG. 3.

During subsequent operation of the boiler (e.g., after time t3), setpoint optimizer module 118 may receive an indication that the HVACsystem is receiving insufficient heat. In response to the indication,the set point optimizer module may determine a possible (e.g., feasible)increase of the supply water temperature set point and a possibleincrease of the pump speed set point that, in combination, would providesufficient heat to the HVAC system. However, as previously describedherein (e.g., in connection with FIGS. 1A and 1B), these set pointchanges may need to be made incrementally. As such, the set pointoptimizer module may first increase the supply water temperature setpoint at time t4, and then, after a delay (e.g., for the supply watertemperature to heat to the increased set point), increase the pump speedset point at time t5, as illustrated in FIG. 3.

Although specific embodiments have been illustrated and describedherein, those of ordinary skill in the art will appreciate that anyarrangement calculated to achieve the same techniques can be substitutedfor the specific embodiments shown. This disclosure is intended to coverany and all adaptations or variations of various embodiments of thedisclosure.

It is to be understood that the above description has been made in anillustrative fashion, and not a restrictive one. Combination of theabove embodiments, and other embodiments not specifically describedherein will be apparent to those of skill in the art upon reviewing theabove description.

The scope of the various embodiments of the disclosure includes anyother applications in which the above structures and methods are used.Therefore, the scope of various embodiments of the disclosure should bedetermined with reference to the appended claims, along with the fullrange of equivalents to which such claims are entitled.

In the foregoing Detailed Description, various features are groupedtogether in example embodiments illustrated in the figures for thepurpose of streamlining the disclosure. This method of disclosure is notto be interpreted as reflecting an intention that the embodiments of thedisclosure require more features than are expressly recited in eachclaim.

Rather, as the following claims reflect, inventive subject matter liesin less than all features of a single disclosed embodiment. Thus, thefollowing claims are hereby incorporated into the Detailed Description,with each claim standing on its own as a separate embodiment.

What is claimed:
 1. A controller for a boiler of a heating, ventilation,and air conditioning (HVAC) system, comprising: a memory; and aprocessor configured to execute executable instructions stored in thememory to: determine, using a first model and a second model, a changeto a set point of the boiler that would lower a cost of operating theboiler, wherein: the first model includes a model of a relationshipbetween a plurality of controlled variables of the boiler and aplurality of manipulated variables of the boiler; and the second modelincludes a model of a relationship between the cost of operating theboiler and the plurality of manipulated variables; determine whether thechange to the set point of the boiler is possible for the boiler; andmake the change to the set point of the boiler upon determining thechange is possible.
 2. The controller of claim 1, wherein: the firstmodel includes a look up table that includes values of the plurality ofcontrolled variables of the boiler for different values of the pluralityof manipulated variables of the boiler; and the second model includes alook up table that includes the cost of operating the boiler fordifferent values of the number of manipulated variables.
 3. Thecontroller of claim 1, wherein the processor is configured to executethe instructions to determine the first model based on: a supply watertemperature set point of the boiler; a return water temperature of theboiler; and a pump speed of the boiler.
 4. The controller of claim 1,wherein the processor is configured to execute the instructions todetermine the second model based on: a firing rate of the boiler; a pumpspeed of the boiler; a fuel consumption of the boiler; and a price ofthe fuel consumed by the boiler.
 5. The controller of claim 1, whereinthe processor is configured to execute the instructions to: determine afiring rate of the boiler that generates a particular supply watertemperature of the boiler using the first model; and determine the costof operating the boiler at the determined firing rate using the secondmodel.
 6. The controller of claim 1, wherein the processor is configuredto execute the instructions to update at least one of the first modeland the second model during operation of the boiler.
 7. A method ofoperating a boiler of a heating, ventilation, and air conditioning(HVAC) system, comprising: determining, by a controller of the boilerusing a first model and a second model, changes to a plurality of setpoints of the boiler that would lower a cost of operating the boiler,wherein: the first model includes a model of a relationship between aplurality of controlled variables of the boiler and a plurality ofoperating conditions of the boiler; and the second model includes amodel of a relationship between the cost of operating the boiler and theplurality of operating conditions of the boiler; and making, by thecontroller of the boiler, the changes to the plurality of set points ofthe boiler, wherein the changes to the plurality of set points are madeincrementally.
 8. The method of claim 7, wherein: the first modelincludes a look up table that includes values of the plurality ofcontrolled variables of the boiler for the plurality of operatingconditions of the boiler; and the second model includes a look up tablethat includes the cost of operating the boiler for the plurality ofoperating conditions of the boiler.
 9. The method of claim 7, whereinthe method includes tracking the changed set points of the boiler usingthe first model.
 10. The method of claim 9, wherein tracking the changedset points of the boiler includes ensuring the plurality of controlledvariables of the boiler are maintained at the changed set points duringoperation of the boiler.
 11. The method of claim 7, wherein the methodincludes: determining the first model and the second model based oninitial values for the plurality of controlled variables of the boilerand the plurality of operating conditions of the boiler; and updatingthe first model and the second model based on updated values for theplurality of controlled variables and the plurality of operatingconditions during operation of the boiler.
 12. The method of claim 7,wherein the method includes generating the first model by plotting anumber of data points in a graph, wherein each data point represents asupply water temperature, return water temperature, and firing rate ofthe boiler at a different point in time during operation of the boiler.13. The method of claim 7, wherein the second model includes: a plot ofthe cost of operating the boiler at different firing rates of theboiler; and a plot of the cost of operating the boiler at different pumpspeeds of the boiler.
 14. A heating, ventilation, and air conditioning(HVAC) system, comprising: a boiler; and a controller for the boiler,wherein: the controller includes: a first model, wherein the first modelincludes a model of a relationship between a controlled variable of theboiler and: a plurality of manipulated variables of the boiler; and aplurality of operating conditions of the boiler; and a second model,wherein the second model includes a model of a relationship between acost of operating the boiler and: the plurality of manipulated variablesof the boiler; and the plurality of operating conditions of the boiler;and the controller is configured to: determine, using the first modeland the second model, a change to a set point of the controlled variableof the boiler that would lower the cost of operating the boiler; andmake the change to the set point of the controlled variable of theboiler.
 15. The HVAC system of claim 14, wherein: the first modelincludes a function of the controlled variable of the boiler and theplurality of manipulated variables of the boiler and the plurality ofoperating conditions of the boiler; and the second model includes afunction of the cost of operating the boiler and the plurality ofmanipulated variables of the boiler and the plurality of operatingconditions of the boiler.
 16. The HVAC system of claim 14, wherein thecontroller is configured to determine of the first model and the secondmodel based on real time operational data of the boiler.
 17. The HVACsystem of claim 16, wherein the real time operational data of the boilerincludes: a supply water temperature of the boiler; a return watertemperature of the boiler; a pump speed of the boiler; and a firing rateof the boiler.
 18. The HVAC system of claim 14, wherein the controlleris configured to receive at least one of the first model and the secondmodel from a user of the controller.
 19. The HVAC system of claim 14,wherein at least one of the first model and the second model is apre-engineered model.
 20. The HVAC system of claim 14, wherein thenumber of operating conditions of the boiler include a constantoperating condition of the boiler.